Compositional Characterization of Phase-Separated Pine Wood Slow Pyrolysis Oil by Negative-Ion Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

The chemical composition of slow pyrolysis oil made from unbarked Scots pine (Pinus sylvestris) was characterized by negative-ion electrospray ionization Fourier transform ion cyclotron resonance (ESI FT-ICR) mass spectrometry and various bulk analyses. The wood pieces were heated stepwise in a batch pyrolysis reactor to the target temperature of 320 °C. The resulting pyrolysis oil spontaneously separated into aqueous and oily phases. The water content of the aqueous phase was as high as 60.4 wt %, whereas for the oily phase it was only 8.1 wt %. The bulk O/C ratio (on a dry basis) was more than twice as high for the aqueous phase as compared to the oily phase (0.61 vs 0.29), suggesting different chemistry between the two phases. On the basis of pH and total acid number measurements, the aqueous phase was more acidic than the oily phase. The ESI FT-ICR technique was used to characterize pyrolysis oils’ heavier, nonvolatile, and thermally labile species. The total amounts of the identified chemical formula...